(1) Field of Invention
The present invention is concerned with the utilization of all tubers of family Convolvulaceae, including tubers at least more deeply colored than light-fleshed tubers, including yellow and orange varieties, and including regardless of color, varieties with firm flesh and varieties with moist flesh, with the purpose of producing various flours from the tubers, and other valuable edible products and industrial products.
The present invention is concerned with the utilization of tubers at least more deeply colored than light-fleshed tubers in the family Convolvulaceae, including yellow and orange varieties, and including regardless of color, varieties with firm flesh and varieties with moist flesh, with the purpose of producing various flours from the tubers and other valuable edible products and industrial products.
The present invention is concerned with the utilization of orange sweet potato tubers in the family Convolvulaceae, with the purpose of producing various flours from the tubers and other valuable edible products and industrial products.
(2) Description of The Background
Products of dried orange sweet potatoes are well known, and have been reported in the patent literature as early as the 1840's. Dried, ground orange sweet potatoes were patented for use as an ingredient in a coffee blend (U.S. Pat. No. 100,587 issued in 1870) because these dried orange sweet potatoes look and taste like burned bricks. The caroteen pigment seems to have concentrated during drying and to have caused a disagreeable taste and color. The other patented uses of orange sweet potato flour are limited primarily to that of rehydratable powders primarily for use in orange sweet potato pie or pumpkin pies. This is probably due to the strong taste of orange sweet potato flours of the prior art and the fact that when rehydrated, these orange sweet potato flours lose cohesion, and will not keep a shape or hold trapped air.
Uncooked orange sweet potato flour made by the methods of Marshall (U.S. Pat. No.77.995), and Baylor (U.S. Pat. No. 100,587) produced a flour considered inferior. The orange sweet potatoes tended to darken during dehydration; this darkened flour could not be rehydrated to make a good tasting substitute for the original fresh product, and the flour tended to have a very strong bitter taste, particularly when produced by the method of Baylor. Because of the inferior properties of uncooked orange sweet potato flour, in the late 1800's and early 1900's the field as a whole turned emphasis away from uncooked to cooked orange sweet potato flours. In the only mention of uncooked orange sweet potato flour since then, it is described as cattle fodder by Ware (Possibilities in New and Extended Uses of the Sweet Potato, Alabama Agricultural Experiment Station, 9 p., 1941).
Until the instant invention, no orange sweet potato flour, whether uncooked or cooked, has been able to be used as a substitute for more than about 30% of a wheat dough without significant deterioration in texture risen structure, and taste. Even when a 15-85 mixture, by weight, of orange sweet potato flour and wheat flour was used, the resulting bread product was significantly lower in specific volume. At ratios of 20-80 by weight of orange sweet potato flour and wheat flour, the specific volume of the bread product was reduced by about 50 percent.
Other investigators have added cooked orange sweet potato flour to many products such as cookies, cakes, candies, ice cream, breads, and the like. In not one case was it possible to develop a product with orange sweet potato flour as the primary ingredient. It was only possible to add small amounts of cooked orange sweet potato flour to existing recipes containing conventional ingredients. The result was to produce previously known products having orange sweet potato flavor and color.
In my early research on sweet potatoes I tried making and using flours of orange sweet potatoes. The color of the flour was very dark, and the flavor of the uncooked orange sweet potato flour was very strong, as was described by other investigators. When I tried to use the flour to prepare pancakes and the like, the products fell apart in much the same way that fresh orange sweet potatoes tend to fall apart when they are cooked. In agreement with the teachings of the art. I was unable to prepare any products from orange sweet potato flour alone.
I then began to work with white sweet potatoes. In my early research on white sweet potato flour, the white sweet potato flour was made by a high speed impact grinding method which produced a flour of wide particle-size distribution, with the fibrous portions of the tuber remaining in the larger particle sizes, and rendering the flour unsuitably heavy and gritty. When screened. (as is accepted practice in the art to obtain a fine flour) the larger particles (representing about 1/2 or more of the total weight of the comminuted meal) were removed; this produced a lighter and less gritty flour, but one poorly suited for producing breads and other products where consistency and lightness are important. Applicant found that by eliminating the high impact grinding method, a more uniformly fine flour which incorporated a greater proportion of the plant fiber into the flour was produced, thus greatly improving the ability of the doughs to hold a rise and produce consistently uniform products.
In addition white sweet potato flour was made by soaking white sweet potato tubers in water between the peeling and drying steps. This produced shreds with a high moisture content that made them susceptible to spoilage during dehydration and produced sour-tasting inferior products that spoiled easily. It was found that the soaking step could be eliminated thus eliminating spoilage problems during drying steps and producing a flour of better taste. lower moisture content, and better baking properties.
I then developed a new process for preparing white sweet potato flour which involved reducing moisture content, incorporating more fibrous and other non-farinaceous material into the flour, and obtaining a whole, moderately fine or finer flour. This flour had improved storage capability and provided products of palatable consistency. This white sweet potato flour was suitable for use in baked and other products, and it was possible to develop new processes. different from conventions of the art, which made it possible to use the white sweet potato flour of the instant invention to prepare products with properties and characteristics previously only obtainable from products containing wheat and other grains, legumes, eggs, milk, nuts and the like.
I continued to work with white sweet potatoes exclusively, and developed improved processes. I found that flours retaining most of the substance of the tuber or sweet potato, preferably substantially all of the substance of the tuber or sweet potato, most preferably all of the substance of the tuber or sweet potato, provided a flour with improved properties.
Similarly, I found that including most of the flesh and fiber of the tuber or sweet potato, preferably including substantially all of the flesh and fiber of the tuber or sweet potato, most preferably including all of the flesh and fiber of the tuber or sweet potato, provided a flour with improved properties.
Similarly, I found that flours which in addition to containing starch retain most of the non-farinaceous substance of the tuber or sweet potato preferably in addition to containing starch retain substantially all of the nonfarinaceous substance of the tuber or sweet potato, most preferably in addition to containing starch retain all of the non-farinaceous substance of the tuber or sweet potato, provided a flour with improved properties.
Similarly, I found that flours retaining most of the starch, insoluble substance, and soluble substance of the tuber or sweet potato, preferably retaining substantially all of the starch, insoluble substance, and soluble substance of the tuber or sweet potato, most preferably retaining all of the starch, insoluble substance, and soluble substance of the tuber or sweet potato, provided a flour with improved properties.
The term `farinaceous` means starch or starchy. In this application, Applicant uses the term `non-farinaceous` to refer to the components of the tuber other than starch. such as protein, soluble and insoluble fractions, fat, vitamins, minerals, and metabolic products. In the context of a flour or dried product, water will necessarily have to be removed, and some volatiles may be lost during drying. The term `non-farinaceous` is used to refer to all components other than starch of a whole, dried tuber.
I further found that obtaining this flour by methods which produced a flour without sifting or with very little sifting provided a flour with improved properties.
Thus I found that a dry, whole flour of white sweet potatoes provided a flour with unique properties not obtained before, and one which without the addition of other flours, chemical modifiers, dough strenghtheners, or other foods such as milk, legumes, eggs, sugar, and yeast, could be used to prepare baked products of risen structure that were previously not possible. In other words. the flour alone with no other additives can be used to prepare a dough capable of holding a rise, and is suitable for preparation of baked products of risen structure that were previously not possible.
This is not the orange sweet potato flour with which I began my research. The early flour had been prepared according to the conventions of the art, which included a soaking step, incurring large losses (primarily of soluble and insoluble fiber) due to removal of thick peels, drying at high enough temperatures to provide for carmelization and charring of portions of the sweet potato, obtaining a fine flour by processes of repeated sifting which resulted in the loss again of fibrous material.
After defining the properties for obtaining flour from white sweet potatoes, I began to wonder whether the properties thus obtained would be sufficient to overcome the more hygroscopic nature of orange sweet potatoes, their tendency to carmelize, and the lack of structure upon combining with water.
I therefore prepared a flour of orange sweet potatoes by the method used to obtain the white sweet potato flour, and used the flour in processes for baking bread and other products. To my surprise I found that the flour was not the color of bricks but rather was a very light orange color, did not have the flavor of burned bricks but rather had a very pleasant, slightly sweet, sweet potato flavor. I found that when I used the flour to prepare a bread, the identical proportions and steps described for white sweet potato flour also produced a wonderful-tasting orange sweet potato bread. The risen structure of the bread was at least equal to that of the white sweet potato bread and possibly was slightly higher than that of white sweet potato bread. The color was definitely a bright orange, and the flavor was definitely that of sweet potato; however, without any other ingredients (eg the sugars and spices so often used) the flavor of the bread was very pleasant and satisfying without being overpowering.
In my subsequent research, I have found that contrary to my own teachings, I have been able to obtain a flour from orange sweet potatoes with properties that are sufficient to provide a risen structure to baked products without the addition of any agents for dough strenghthening, without chemical modifiers. and without any added ingredients such as wheat or other grains, eggs, legumes, milk, fat, yeast, or the like.
This orange sweet potato flour, like that for white and light-fleshed sweet potato flours can be used as a complete substitute for milk, eggs, wheat and other grains, legumes, sugar, and the like. I have found that the processes developed for white sweet potatoes and light-fleshed sweet potato varieties provide products of equal properties when orange sweet potatoes are used in these processes. The proportions and processes are generally the same. Thus the methods for making flour and the processes for obtaining a wide variety of products are equally applicable to all types of sweet potatoes and other tubers in the morning glory family, Convolvulaceae, independent of color, and independent of firmness or moistness of flesh.